Mixtures of isomeric decyl alcohols, phthalates obtainable therefrom, and their use as plasticizers

ABSTRACT

Mixtures of isomeric decyl alcohols obtained by oligomerization of propylene in the presence of deactivated zeolites as catalysts, followed by separation of the nine carbon olefins from the oligomer mixture, then hydroformylation of the 9 carbon olefins to 10 carbon aldehydes, and hydrogenation of the aldehydes to the corresponding alcohols. The mixtures, when esterified with phthalic acid, or anhydride, provide a mixture of isomeric di-decyl phthalates that can be used as plasticizers.

PRIOR APPLICATION

This application is a continuation of U.S. patent application Ser. No.08/083,631 filed Jun. 28, 1993, now abandoned.

This application claims the priority of German application P 42 21472.6, filed Jun. 30, 1992.

The present invention relates to mixtures of isomeric decyl alcohols, toa process for their preparation, to the phthalates obtained from thesealcohols, and to their use as plasticizers.

BACKGROUND OF THE INVENTION

Esters of phthalic acid are used in large amounts as plasticizers, inparticular for polyvinyl chloride. The alcohol components arepredominantly primary alcohols having 8 to 10 carbon atoms, of which2-ethylhexanol is currently the most important. Phthalates formed fromshorter-chain alcohols provide plasticizers having a good gellingstrength. However, their greater volatility is a disadvantage comparedto longer-chained compounds. Longer-chain esters, on the other hand, gelmore slowly and have less resistance to low-temperatures.

The properties of phthalate plasticizers are influenced by the size ofthe alcohol molecule and also by the branching of the carbon chain. Forexample, alcohols with few branches produce ester plasticizers that areparticularly valued despite their high low-temperature flexibility.Predominantly linear alcohols having 9 to 10 carbon atoms in themolecule are therefore becoming increasingly important as the alcoholcomponents. A precondition for their use is that they are available inlarge amounts and are relatively inexpensive.

Throughout the specification and claims, all percents are by weightunless otherwise indicated. According to German Patent 2 855 421, theplasticizers used are phthalates of alcohols having 9 carbon atoms,which are obtained by the oxo reaction of 8 carbon olefins,hydrogenation of the reaction product, and esterification of theresulting 9 carbon alcohols with phthalic anhydride. From 3% to 20% ofthe starting olefins should have an isobutane skeleton in each molecularchain, less than 3% of the olefins contain quaternary carbon, and morethan 90% of the total amount of the olefins are present as n-octenes,monomethylheptenes, and dimethylhexenes. Furthermore, the weight ratioof the total amount of n-octenes and monomethylheptenes to thedimethylhexenes should be more than 0.8.

Phthalates based on 10 carbon alcohols are the subject of EuropeanPatent Application 366,089. These alcohols are used as a mixtureobtained by hydroformylation of a butene fraction, aldol condensation ofthe resultant aldehyde mixture, and subsequent hydrogenation.

Another route for obtaining di-decyl phthalate mixtures is described inEuropean Patent Application 424,767. The esters are prepared by amultistage process involving dimerization of butene mixtures,hydroformylation and hydrogenation of the resulting octene mixture toform a nonanol mixture, dehydration of the nonanol mixture to form anonene mixture, and hydroformylation and hydrogenation of the nonenemixture to a mixture of decanols.

The known processes still do not satisfy, as regards economic andtechnical aspects, all requirements that are placed on a processemployed on a large scale. The starting materials are not available insufficient amounts, they are too expensive, and/or the conversion of thestarting materials into the alcohols involves processes that are toocomplicated. The object of the invention is, therefore, to develop aprocess that starts from raw materials that are available at areasonable price and which can be converted into the desired alcohols ina technically simple manner.

SUMMARY OF THE INVENTION

A portion of the invention consists of mixtures of isomeric decylalcohols, and a method of their preparation. These decyl alcohols areobtained by oligomerization of propylene in the presence of deactivatedzeolites as catalysts, followed by separation of the 9 carbon olefinsfrom the oligomer mixture formed, then hydroformylation of the mixtureto 10 carbon aldehydes, and hydrogenation of the aldehydes to thecorresponding alcohols.

DETAILED DESCRIPTION OF THE INVENTION

The carbon olefins used as starting materials for the preparation of themixtures of isomeric decyl alcohols of the invention are the product ofthe oligomerization of propylene in the presence of deactivatedzeolites. The oligomerization of low molecular weight olefins, such aspropylene, n-butene, i-butene, n-pentene, under the action of specialzeolites is a known reaction, and is described, for example, in U.S.Pat. No. 4,982,031. The catalytically active zeolites are preferably ofthe ZSM-5 type, the surfaces of which have been deactivated with asterically hindered base, e.g. a trialkylated pyridine. When propyleneis used as the olefin, for example, an oligomer mixture comprisingessentially monoolefins having 6, 9, 12, 15, 18, and 21 carbon atoms areproduced. It is particularly significant that these olefins are largelyunbranched. Based on the compounds of different molecular size in theoligomer mixture, there are only about one to two methyl branches forevery 15 carbon atoms arranged in an unbranched chain. Due to the lowdegree of branching, the 9 carbon olefins obtained as describedhereinbefore differ recognizably from the propylene oligomer termedtripropylene, which is prepared from propylene in the presence of acidcatalysts, in particular phosphoric acid or sulfuric acid, and whichcomprises a mixture of highly branched nonenes.

To isolate the 9 carbon olefins which are intended to be processedfurther, the oligomerization product is separated in a conventional wayby distillation into individual fractions. The nonene fraction that isobtained can be hydroformylated without additional purification stages.

The hydroformylation of the 9 carbon olefin mixture is carried out bythe prior art processes in the usual manner, using cobalt as well asrhodium as the catalyst. The reaction can be carried out in thehomogeneous liquid phase, with catalysts that are soluble in organicmedia, or can be carried out in heterogeneous reaction systems, withcatalysts that are dissolved in water. The latter procedure has beenfound to be particularly suitable in conjunction with rhodium catalysts.

In the case of hydroformylation in homogeneous reaction systems, theconventional process with cobalt catalysts is used. Temperature of 90°C. to 150° C., pressures of 10 to 30 MPa, and catalyst concentrations of0.1% to 1.5% of cobalt, based on the olefin employed, are the standardreaction conditions. Instead of cobalt, the hydroformylation catalystmay also be rhodium, which is substantially more active than cobalt andis therefore used in a lower concentration. The reaction is normallycarried out at 80° to 200° C. and pressures of 10 to 60 MPa. 0.1 to 50mg, preferably 2 to 10 mg, of rhodium is used per kg of olefin. Aneffective catalyst compound in both cases is hydridocarbonyl HMe(CO)₄,wherein Me is cobalt or rhodium.

Instead of catalyzing the conversion of the olefin mixture to aldehydesusing simple carbonyl compounds, modified carbonyl compounds of cobaltor rhodium may also be successfully used. Modified carbonyl compoundsare compounds of the aforementioned metals which also contain, in themolecule, further complex ligands other than carbon monoxide. Thisvariant of the hydroformylation reaction also belongs, when cobaltcatalysts and rhodium catalysts are used, to the prior art. Preferredcomplex ligands are organic compounds of trivalent phosphorus. Examplesof such compounds are triarylphosphines, such as triphenylphosphine;trialkylphosphines, such as tributylphosphine;tri(alkyl/aryl)phosphines, such as diethylphenylphosphine; triarylphosphites, such as triphenyl phosphite; trialkyl phosphites, such astriethyl phosphite; tri(alkyl/aryl) phosphites; and phospholes. Alsosuitable are bidentate ligands, i.e. diphosphines or diphosphites, whichcontain two phosphorus(III) atoms capable of participating in complexformation; among these compounds those which form chelates with themetal atoms are preferred. Particularly suitable as ligands aresterically hindered phosphites capable of participating in the chelateformation, which form, with the inclusion of the central metal atom,rings containing nine atoms. Such phosphites are described, for example,in EP 353,770 A2 and in EP 435,071 A2.

The ligands are normally used in excess, i.e. in an amount that isgreater than that required for the complex formation. The ratio of metalatoms to ligand molecules (in moles) of 1:5 to 1:100 has been foundsuitable in practice; as is known, this ratio depends on, inter alia,the nature of the ligand. Modified cobalt or rhodium catalysts permitthe use of lower reaction pressures than unmodified catalysts, pressuresof 0.1 to 10 MPa, especially 0.5 to 6 MPa, being customary. The reactiontemperatures, when modified cobalt catalysts are used, are 140° to 180°C.; they are higher than in the case of the corresponding rhodiumcatalysts, which require temperatures of only 90° C. to 130° C. Thesynthesis gas used for the hydroformylation preferably contains aboutequal volumes of hydrogen and carbon monoxide, though variations fromthis composition in either direction are not harmful.

In the heterogeneous phase, the hydroformylation of the 9 carbon olefinsis carried out in a two-phase system, an embodiment of the oxosynthesis, which is described, e.g. in German Patent 26 27 354. Such aprocess is characterized by two liquid phases; namely, an organic phase,which contains the starting olefin and the reaction product, and anaqueous phase, in which the catalyst is dissolved. Water soluble rhodiumcomplex compounds with water soluble phosphines as ligands have beenfound to be suitable as catalysts. Water-soluble phosphines includetriarylphosphines, trialkylphosphines, alkyldiphosphines,aryldiphosphines, and alkylaryldiphosphines, whose organic radicals havebeen substituted by sulfonyl groups or carboxyl groups. The reaction iscarried out at 60° to 150° C., preferably 90° to 120° , and underpressures of 0.4 to 30 MPa, in particular 1 to 10 MPa. The rhodiumconcentration is 20 to 2000 ppm by weight, preferably 50 to 500 ppm byweight, based on the aqueous catalyst solution, and 4 to 100 mol ofwater-soluble phosphine are used per tool of rhodium. The volume ratioof aqueous phase to organic phase is from 0.1 to 10:1.

The olefin conversion is significantly increased if a phase transferreagent (solubilizer) is added to the aqueous catalyst solution.Particularly suitable are cationic solubilizers of the formula [A-N(R¹R² R³)]⁺ E⁻, in which A is a straight or branched chain alkyl radicalhaving 6 to 25 carbon atoms; R¹, R², R³ are individually straight orbranched chain alkyl radicals having 1 to 4 carbon atoms; and E⁻ is anyanion, in particular it is sulfate, tetrafluoroborate, acetate,methosulfate, benzenesulfonate, alkylbenzenesulfonate, toluenesulfonate,lactate, or citrate.

The hydroformylation of the 9 carbon olefins according to the inventionwith cobalt or rhodium as catalyst, which is carried out either in theone- or two-phase reaction system, produces a mixture of isomericdecanals in high yield. This mixture contains 80% or more straight-chain10 carbon aldehydes, and only minor amounts of methyl-branched anddimethyl-branched aldehydes. The composition of the aldehyde mixture canbe influenced by varying the reaction conditions and/or the catalyst, inparticular by the choice of ligand when using modified carbonyls.

After completion of the hydroformylation, the aldehyde mixture isseparated from the catalyst, from the unconverted reactants, and fromthe other reaction products. Distillation is the normal separationprocess when carrying out the reaction in the homogeneous phase. If thehydroformylation was carried out in the two-phase system, the productand catalyst can be recovered merely by phase separation. This processis substantially simpler in its technical execution and, on account ofthe absence of high temperatures, is also considerably more gentle thanthe distillative isolation of the aldehyde mixture. The hydroformylationof the 9 carbon olefin mixture may be carried out batchwise orcontinuously, irrespective of the process employed.

The isomeric decanals separated from the remaining constituents of thereaction mixture are then hydrogenated to the desired decyl alcoholmixture. The addition of hydrogen is effected in known manner in thepresence of catalysts. Suitable hydrogenation catalysts are, forexample, based on nickel, chromium, or copper. The hydrogenationtemperature is generally from 100° to 180° C., and pressure is 1 to 10MPa; the decyl alcohol mixture is then purified by distillation. Themixture is highly suitable as the alcohol component in phthalates thatare to be used as plasticizers. The preparation of the phthalates isknown [cf. Ullmann, Encyclop adie der Technischen Chemie (1979), Vol.18, p. 536 ff]. Phthalic anhydride is expediently reacted with the decylalcohol mixture in one stage in a molar ratio of 1:2. The reaction ratecan be increased by using catalysts and/or raising the reactiontemperature. In order to displace the equilibrium in the direction ofester formation, the water formed must be removed from the reactionmixture. The phthalates obtained from the decyl alcohol mixtureaccording to the invention are plasticizers characterized by outstandinglow-temperature properties.

The invention is illustrated in more detail in the following example,but is not restricted to this specific embodiment.

EXAMPLE 1. Starting Olefin Mixture

An oligomeric propylene is used that has been obtained by reactingpropylene on a deactivated zeolite as the catalyst. It comprises about87.3% tripropylene and 12.7% tetrapropylene. A high proportion of theolefins is linear, a very small amount being slightly branched.

2. Hydroformylation

500 g of the olefin mixture, 10 g of CoCO₃, and 15 g of water arereacted with water gas (H₂ :CO=1:1) in a 1 liter autoclave at 170° C.and 27 MPa for 4 hours. The autoclave contents are decompressed andcooled, and 52 g of water is added. The autoclave is re-closed andheated to 190° C. for 2 hours with stirring. The contents are cooled andthe organic and aqueous phases are separated from one another. 549 g ofcrude aldehyde is obtained.

3. Hydrogenation

The crude aldehyde is treated with hydrogen in a 2.8 liter autoclave at150° C. and under a pressure of 10 MPa in the presence of a nickelcatalyst (10% by volume, based on the starting materials). The contentsare then cooled, the pressure is released, and the contents arehydrogenated again under the same reaction conditions with the additionof a further 5% by volume of a nickel catalyst. The reactor is cooled,the pressure is released, and the crude alcohol product is separatedfrom the nickel catalyst by filtration.

4. Distillation

825.5 g of the crude alcohol is then distilled in a 1 meter columncontaining glass rings 5 mm in diameter. A first running is removed atan overhead temperature of 100° C. and 13.3 kPa pressure, and anintermediate cut is removed at 135° C. and 6.7 kPa pressure. The mainfraction is obtained at an overhead temperature of 147° C. and 6.7 kPa.Gas chromatography analysis shows an alcohol content of 95.7%; the yieldof pure 10 carbon alcohol, based on the feedstock olefin, is 72% oftheoretical.

5. Esterification

380.4 g (2.3 mol) of the pure 10 carbon alcohol and 148.1 g (1 mol) ofphthalic anhydride are reacted at 135° C. in the presence of 0.59 g ofconcentrated sulfuric acid, the water formed in the reaction beingremoved. The reaction is complete after 6 hours, and the reactionproduct is neutralized with 5% sodium hydroxide solution. Steamdistillation is then carried out at 135° C. and 15 kPa. The distillateis washed with water and then dried for 5 hours in a stream of nitrogenat 135° C and 2 to 3 kPa. After filtration, a clear liquid is obtainedhaving the following characteristic data:

    ______________________________________                                        Ester content       99.41%                                                    Alcohol content     0.22%                                                     Pt/Co color index   5-10                                                      Density (g/ml; 20° C.)                                                                     0.9655                                                    Viscosity (mPa · s; 20° C.)                                                       108                                                       Acid number (mg KOH/g)                                                                            0.06                                                      ______________________________________                                    

The viscosity of the ester is considerably lower than the viscosity ofcurrently available products based on conventional propylene polymers,which is 120 to 130 mPa.s/20° C. The ester is thus notable for itsoutstanding processing properties.

We claim:
 1. A mixture of decyl alcohols which is the product ofoligomerization of propylene, catalyzed by deactivated zeolite, to forman oligomer mixture comprising 9 carbon olefins, separation of said 9carbon olefins from said oligomer mixture, hydroformylation of said 9carbon olefins to 10 carbon aldehydes, and hydrogenation of saidaldehydes to said decyl alcohols, said alcohol mixture being at least80% linear and containing minor amounts of methyl--branched anddimethyl--branched decyl alcohols.
 2. The mixture of claim 1 whereinsaid hydroformylation is carried out in the presence of at least onecobalt catalyst.
 3. The mixture of claim 1 wherein said hydroformylationis carried out in the presence of at least one rhodium catalyst.
 4. Themixture of claim 3 wherein said rhodium catalyst is a complex compoundwhich contains organic phosphines as ligands.
 5. The mixture of claim 4wherein said organic phosphines are water soluble.
 6. The mixture ofclaim 3 wherein said rhodium catalyst is a complex compound whichcontains organic phosphites as ligands.
 7. The mixture of claim 6wherein said organic phosphites are sterically hindered.
 8. A mixture ofisomeric decyl phthalates which are the reaction product of the mixtureof decyl alcohols of claim 1 and a compound selected from the groupconsisting of phthalic acid and phthalic anhydride.